I'am a bit too lazy for formulating an all-encompassing answer, but I'am looking for some quotes. Here we go, those are same quotes from the final chapter of Eric D. Weitz' Weimar Germany. Promise and Tragedy. I would agree to all his major points and would add, that it was similar to Spain before the Civil War.

364: But these freedoms were also deeply contested. Modern art, the new woman, and casual sex were all flash points of conflict that were piled on top of the plain hatred of democracy that the large, multitudinous right wing continually articulated. Ultimately, the opposition would prove too great for Weimar freedom. But Weimar did not just die as if there were some anonymous process at work, as if there is some undefined moment when a volume of social conflict reaches a crescendo and everything comes crashing down. Weimar did not just collapse; it was killed off. It was deliberately destroyed by Germany’s antidemocratic, antisocialist, anti-Semitic right wing, which, in the end, jumped into political bed with the Nazis, the most fervent, virulent, and successful opposition force.

365: But the collective hostility of those who commanded Germany’s resources, staffed its major institutions, and found a democratic, socially minded, and culturally modern and innovative society intolerable—those are the people who destroyed the republic and without whom the Nazis would never have come to power.

365f: Weimar’s history does show us that a society lacking consensus, a society in which no set of ideas and no group constitute hegemony, can be a dangerous place. A democratic political system cannot long endure a situation in which virtually every issue becomes magnified to an ideological contest over ultimate meanings. But it especially cannot endure when its elites seek to undermine the democracy from within, when they whine incessantly about a system in which they still exercise privileges and still dispose of immense resources. Weimar cautions us about the conditions in which democracy can flourish. It would be hard to think of more inauspicious circumstances for the founding and flowering of a democracy than those of post– World War I Germany. The burdens of the lost war, revolution and civil war, economic crisis—even in a society with a well-rooted democratic culture, such conditions would put democratic convictions and democratic practices to hard tests. People desire security—protection of their very lives and of their economic well-being. When a democratic system cannot provide those basic requirements, even the best democrats may edge away from it and look to more authoritarian solutions. Weimar also demonstrates the limits of elections as a criterion for democracy. Weimar had its elections, to be sure, and they were democratically contested. But it also had a highly conservative judiciary that rarely punished right-wing militarists and terrorists, while it gleefully interned and convicted left-wing activists. Weimar had a bureaucracy that, despite the influx of Social Democrats and liberal Catholics, remained in many offices deeply opposed to democracy. And it had a business class whose commitment to the republic was tenuous at best. Democracy needs democratic convictions and a democratic culture that ripple through all the institutions of society, not just the formal political ones. That was hard to find in many of the key institutions of the republic. Weimar’s problem was not so much a popular democratic deficit, because the bastions of the republic were to be found primarily among workers, reform-minded Catholics, artists and writers, and some members of the professions. The major institutions like the churches, the army, schools and universities, and industrial organizations were largely hostile or recklessly indifferent to the republic, and those institutions were at the upper levels populated by the well connected and the powerful.